This proposal seeks to extend our previous studies on schistosomula of S. mansoni in two directions. First, we wish to explore the functional role of the membrane fusions which we initially described between human neutrophils and schistosomula. The fusions appear as hybrid membranes derived from the neutrophil plasma membranes and the outer tegumental membranes of the worm. We wish to test whether these fusions may be the route by which the parasite acquires host membrane components. In brief, we wish to radiolabel neutrophil plasma membranes with iodine and test by electron microscope autoradiography and polyacrylamide gel electrophoresis whether any or all of the labeled proteins are transferred from the cells to the parasites. We will also test whether membrane fusion alters the concentration of intramembrane particles (IMPs) in the outer tegumental membrane. Since IMPs are indicative of the protein concentration of a membrane, a net increase in IMP concentration in the outer membrane would suggest that membrane proteins have been transferred from the cells to the parasites. Finally, we shall attempt to localyze human neutrophil membrane proteins including HLA both within the membrane fusions and after the fused cells have been disrupted. These proteins will be localized by both electron microscopic and new semi thin section immunocytochemical techniques. A second major line of experiments will examine the transformation of cercariae to schistosomula because the surfaces of both organisms are poorly defined structurally, chemically, and immunologically. We hope to determine the chemical composition of the cercarial glycocalyx, how it is lost, whether any of it is retained on transformed schistosomula, and whether shed glycocalyx will bind to transformed schistosmula. In addition, we hope to label the cercarial membrane in order to test its chemical composition, how much of it is lost during transformation, how it is lost, and how much is retained on transformed schistosomula.